Precast concrete structural unit



Aug. 9, 1932. R. F. GREENWOOD 1,871,318

PRECAST CONCRETE STRUCTURAL UNIT v Filed Jan. 5o, 1929 4 'f' 'l @www ATTORNEY l Patented Aug. 9, 1932 UNITED s'rares LLaziale RICHARD F. GREENWOOD, lOl? NEW YORK, N. Y.

IREGAST CONCRETE STRUCTURAL UNIT Application filed January 30, 1929. VSerial No. 336,045.

This invention relates to improvements in pre-cast concrete structural units.

It is well known that in concrete T-beam construction, the strength against bending 5 moments toi-tional strain and shearing stresses which may be developed under load depends largely upon the strength of the reinforcement, the arrangement of the same within the T-beam and the strength of the bond between the concreteV and the metallic reinforcement.

The principal object of this invention is to produce a pre-cast T-beam or pre-cast ribbed concrete unit for use in building and like construction Yin Vwhich the reinforcement and concrete surrounding the same will be so correlated. arranged and bonded as tov provide a combined .steel and cement fabrication of great strength along the lines which are usually'weakest and'fwhere failures or cracks in the concrete usually appear. v

Still another object of the invention is to providea pre-cast concrete structural unity in which the metallic reinforcing member ii will have sufcient independent strength and rigidity to constitute an independent loadcarrying element and at the same time will be relatively light, and will have a thorough interlocking bond connectionwith the concrete 'portion of the unit in addition to the usual adherent bond of the concrete and steel.

Still another object of my invention is to provide in a pre-cast T-beam vunit a rigid metallic reinforcing element composed of perforated sheet metal traversing the iiange or plate portion and having an integral deep channel or stirrup portion extending within the rib,.rste1n orbeam section to provide a reinforcing connection between the flange or,

plate and the beam or rib of the unit.

Still another object of my invention is to bend the walls of the channel portion of said reinforcement withiny the rib or 'beam section'to cause them to curve or incline outwardly in relation to the center line of the saidrib or beam section andto merge` with Vthe flange or plate portion in a relatively- `wide arcuate section extending 'closely ad'- .jacent to or crossing the intersection of planesl coincidingyor corresponding to the lower surface of the flangeV section and the sides yof the beam or rib section.

Still another object of my invention is to provide, in a pre-cast T-beam having the conj tinuous perforated sheet metal reinforcement 55u hereinabove described, for further strengthening of the construction and for a symmetrical disposition of the concrete and steel parts thereof by the use of a lillet or web of concrete `or like cementitious material arranged 601 at the junctions or corners between the surfaces of the rib andV flange, thus producing a symmetrical and homogeneous structural unit. i

Still another object of my invention is to provide at the side edges suit'able'bonding grooves and space between adjacent members or succession ofunits within which the metallic reinforcementl from Vthe respective units project and are bonded together to produce a continuous monolithic construction.

l/V ith these and other objects in view,the invention comprises the combination of members and arrangement'of parts so combined as to co-act andcooperate with each other in the performance of the functions and the accomplishment of the results herein contem-l plated, and comprises in one of' its adaptations the species or preferred*` form illustrated in the vaccompanying drawing, in, which l Fig; lis a cross-sectionof two T-beamsor units arranged adjacent to each other;

Fig. 2 is a view, in perspective, of'my re-V inforcing element separate from the beam; F is a plan or top View of a plurality of sections bonded together; and v Fig. 4 vis a diagrammatic view showing how the placement of my reinforcing element transversely traverses the usual diagonal cracks or failures in T-beams. Referring now to the drawing, which illustrates a preferred embodiment of my invention, l indicates a precast ribbed concrete unit or T-beam embodying a flange or plate portion 2 and a rib or beam portion 3 projecting at substantially right angles therefrom. The unit is reinforced by a continuous metallic reinforcement comprising a perforated metal plate 4 bent intermediate,

ico

' stantially right angles to the center line of the channel 4e formed by said channeled portion 4.

This reinforcing element When'bent, as aforesaid, has considerable -independent loadcarrying strength and rigidity and because of the character of the material will enable a thorough bonding and lnterloclnng between the metal and the concrete to be pro'- cured. Furthermore byreason of its continuity, the integrality of its parts and its placement within the concrete T-beam, I am enabled to reinforce and prevent failure at the junctions between the flange or plate and rib or beam sections, which portions of T- beams are weakest and usually fail first under torsional or shearing stresses.

As illustrated this reinforcing element is so placed andvembedded Within the concrete as to cause the metallic flange portions 4d, 4d to extend substantially parallel to the center line of the plate or flange section 2, the integral open-looped stirrup or channel portion 4 to be arranged centrally Within the rib orbeam sections 3 With the bottom 4'EL of the channeled portion extending to a plane adj acent to the outer edge of said rib or `beam section, the opposite Walls 4b of the channel inclining outwardly to opposite sides of the centerline of the rib or beam section and the arcuate portions 4, 4c` of thereinforcement extending to a plane closely adj acent to or crossing the intersection of planes coinciding with the lower surface of the flange and theopposite faces of the rib and thus passing in a substantially transverse direction over diagonal lines extending from said intersection which is the Weakest portion of the unit and along which cracks or failures caused by the contraction of the cement While setting or curing'from the inundated stage to the final setting stage, usually occur.

, Furthermore, I preferably strengthen the bond between said rib and plate or flange portions of the unit by applying at the junctions therebetween a llet or binding web 5 of cementitious material. The thickness of this concrete fillet 5 outside the arcuate portion of the metallic reinforcement at such corners is at least equal to the depth or thickness of the concrete adjacent to the straight flange portions at the same sideof the said reinforcement. Y

The above will be clear from an examination of Fig. 4 in which I have shown infull lines an ordinary T-beam with cracks at the junctionbetweenthe flange andrib members and .have illustrated in dotted lines the positionin g of my reinforcing element in a transverse direction across these cracks and have also illustratedin dotted lines the addition of my fillet which combined with my reinforcing element provides a symmetrical construction of great strength.

In the embodiment shown in Figs. 1 to 3 ,the rflange portion is provided with a bonding groove Qand the reinforcing element 4 has a marginal portion 4f projecting into said groove. When units are assembled, as shown in Fig. 3, they are spaced apart as illustrated at 7 and the bond thus connects the adjacent Vreinforcements as Well as the concrete parts.

After bonding together, a top layer 8 may be applied as shown in said Fig. 3.

1 I also embed in the concrete within the groove or channel 4 a reinforcing rod 6 extending longitudinally of the saidA channel 4- and of the rib portion 3.

` Having described my invention, I claim-:-.

l. A pre-cast concrete structural unit comprising a beam substantially T-shaped in cross section and composed of concrete flange and rib sections and a rigid continuous perforated metallic reinforcing element composed of sheet metal and having independent load-carrying strength and provided at opposite ends with flange portions embeddedin the said concrete flange Vportions of the beam, and a channel portionV substantially V-shaped in cross section formed integrally with said flange portions and extending into .andp'embedded within the said ribV portion.

2. A pre-cast concrete structural unit com-A prising a beam substantially T-shaped in crossisection and composed of concretellange and rib sections and a rigid continuous perforated metallic reinforcingelement composed of sheet metal and having independent loadcarrying strength and Vprovided at opposite ends with flange portions embedded in the said concrete flange portions of the beam, ai

channel portion substantially V-shaped 'inV cross section formed integrally with said flange portions and extending into and embedded Within the said rib portion, the'intermediate channel and flange portions of said reinforcing element merging by arcuate web portions branching in opposite directions, and extending across the junctions formed between the rib and flange portions.

3. A' pre-cast concrete structural unitcomprising a beam substantially T-shaped in cross section andl composed of concrete flange and rib sections and a rigid continuous per forated metallic reinforcing elementV com-v posed of sheet metal and having independentV load-carrying strength and provided at opposite ends With flange portions embedded in the said concrete flange portions of the beam, and a channel portion substantially V-shaped in cross section formed integrally With saidl Y flange portions and extending into andv em bedded Within they said rib portion, the said intermediate Vchannel portion having Walls inclining outwardly away from the center line of the concrete rib and merging with the flange portions by an arcuate web portion extending closely adjacent to the line of intersection of planes which coincide with the bottom surfaces of the flange portions and with the side surfaces of the rib.

4. A pre-cast concrete structural unit com-V prising a beam substantially T-shaped in cross section and composed of concrete flange and rib sections and a rigid continuous perforated metallic reinforcing element composed of sheet metal and having independent load-carrying strength and provided at opposite ends with flange portions embedded in the said concrete flange portions of the beam, a channel portion substantially V-shaped in cross section formed integrally with said flange portions and extending into and embedded within the said rib portion, the said intermediate channel portion having walls inclining outwardly away from the center line of the concrete rib kand merging with the flange portions by an arcuate web portion extending closely adjacent to the line of intersection of planes which coincide with the bottom surfaces of the flange portions and with the side surfaces of the rib, and a concrete fillet arranged adjacent to said arcuate metallic web and filling space at the junction of saidvflanges with the sides of said j rib.

5. A pre-cast concrete structural unit comprising a concrete beam substantially T- shaped in cross section and composed of concrete flange Vand rib sections7 and a continuous rigid plate of perforated sheet metal bent to provide at opposite ends liange sections embedded in the concrete flange sections of the T-beam and an intermediate integral channel portion, substantially 1l-shaped in crosssection, embedded centrally in the rib portion of said unit, each of said flange portions having bon ding grooves along the side edges thereof and said metallic reinforcement having a marginal portion projecting outside the concrete iiange and into said groove to provide an interlock between units.

In witness whereof, I have signed my nam to the foregoing specication.

RICHARD vl?. GREENWOOD. 

